Upright control system for use in a lift truck



Dec. 30, 1969 H. J. THOMAS 3,486,333

UPRIGHT CONTROL SYSTEM FOR USE IN A LIFT- TRUCK Filed March 26, 1968 2 Sheets-Sheet l :3 28 FIG. I 86 gt, 26 \\J INVENTOR HENRY J. THOMAS ATTORNEY H. J. THOMAS Dec. 30, 1959 UPRIGHT CONTROL SYSTEM FOR USE IN A LIFT TRUCK Filed March 26, 1968 2 Sheets-Sheet 2 FIG. 3

ATTORNEY United States Patent 3,486,333 UPRIGHT CONTROL SYSTEM FOR USE IN A LIFT TRUCK Henry J. Thomas, Battle Creek, Mich, assignor to Clark Equipment Company, a corporation of Michigan Filed Mar. 26, 1968, Ser. No. 716,239 Int. Cl. F!) 15/18; B66b 9/20 US. Cl. 6052 11 Claims ABSTRACT OF THE DISCLOSURE A lift truck having an upright extendible at a low speed or a high speed and controls for extending the upright at a low speed only above a predetermlned extension.

BACKGROUND OF THE INVENTION The art to which this invention relates includes elevators, and more specifically portable elevators.

A principal object of my invention is to increase the safety of operation of an upright.

SUMMARY OF THE INVENTION In carrying out my invention in a preferred embodiment, I provide an upright control system including a first control circuit for actuating the upright to extend at a low speed, a second control circuit connected to the first circuit for actuating the upright to extend at a high speed and a third control circuit connected to the first circuit for actuating the upright to lower. The system also includes means disposed in the first circuit and responsive to upright extension for stopping upright extension when the upright is extended a predetermined distance and a fourth control circuit connected to the third circuit for bypassing the stopping means and actuating the upright to extend at low speed only.

The above and other objects, features and advantages of my invention will be readily understood by persons skilled in the art when the following detailed description is taken in conjunction with the drawing.

DESCRIPTION OF THE DRAWING FIGURE 1 is a side elevation of a lift truck embodying my invention,

FIGURE 2 is a schematic of the fluid circuitry associated with the fluid motor of the upright, and

FIGURE 3 is a schematic diagram of the control systern.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, the' reference numeral 10 denotes generally a lift truck of the so-called order picker type. Lift truck 10 includes a body 12 which is supported by a rear drive-steer wheel 14 and a pair of tandem outrigger wheels 16 (only one pair is shown). Mounted on body 12 is a fluid reservoir 18, a power source or battery 20 which is disposed above reservoir 18 and a telescopic upright 22 which is extendible in a conventional mannerby means of a single acting piston and cylinder type fluid motor 24.

Upright 22 includes a fixed mast 26, an intermediate slide 28 telescoped in mast 26 for vertical reciprocal movement therein, an inner slide telescoped in intermediate slide 28 for vertical reciprocal movement therein and a carriage 32 which is connected to inner slide 30 for vertical reciprocal movement therealong. Upright 22 is conventional, and so will not be described in detail further. If further information is desired, reference may be had to US. Patent No. 3,213,967. Fixed to carriage 32 of upright 22 is an operators station 34 and a pair of load 3,435,333 Patented Dec. 30, 1969 engaging members or fork arms 36 which extend forwardly past operators station 34, as shown.

Operators station 34 includes a platform 38 upon which the operator can stand, a control console 40 at which the various vehicle controls, including steering control wheel 42, are located. Operators station also includes a pair of side guards 44, an overhead guard 46 and a pedal 48 which when depressed releases the vehicle brake (not shown) and closes a normally open switch 50 (FIG. 3) so that the various vehicle controls may be energized.

Lift truck 10 normally is operated with the operator standing on platform 38, and from this location the operator can drive the truck in a forward or reverse direction through manpulation of controls at console 40, steer the truck through steering control wheel 42 and raise or lower operators station 34 and load engaging forks 36.

Referring now also to FIG. 2, it will be recalled that extension of upright 22 depends upon extension of fluid motor 24 which may be extended at a low speed or a high speed. Means for extending fluid motor 24 at a low speed includes a fluid conduit 52 which communicates with reservoir 18 at one end thereof and with a flow control valve 54 at the other end thereof, flow control valve 54 communicating with the interior of fluid motor 24. (Flow control valve 54 is conventional and permits unrestricted flow of fluid into fluid motor 24 but restricts fluid flow out of motor 24 at a varying rate which depends upon the load being carried by upright 22, the greater the load the greater the restriction to fluid flowing out of motor 24.) Disposed in conduit 52 is a pump 56 which draws fluid from reservoir 18 and supplies pressurized fluid to motor 24 via valve 54. Pump 56 is driven by means of a pump motor 58 (FIG. 3). Also disposed in conduit 52 upstream of pump 56 is a one-way check valve 60 which prevents fluid from flowing backwards through pump 56 when it is not operational. The means for extending fluid motor 24 at a high speed includes pump 56 and another pump 62 which is connected in parallel with pump 56 by means of a conduit 64 which communicates with conduit 52, as shown. Disposed in conduit 64 upstream of pump 62 is a one-way check valve 66 which prevents fluid from flowing backwards through pump 62 when it is not operational. Pump 62 is driven by means of a motor 68 (FIG. 3).

Upright 22 is lowered by permitting fluid motor 24 to retract. This is accomplished by communicating fluid motor 24 with reservoir 18 so that fluid may flow out of the interior of motor 24 through valve 54 and back into reservoir 18. A fluid conduit 70 is connected between conduit 52 and fluid reservoir 18. Disposed in conduit 70 is a flow restrictor 72 and a solenoid actuated normally closed valve 74. Thus, when valve 74 is actuated to open, fluid in motor 24 can flow therefrom to reservoir 18, thus permitting fluid motor 24 to lower. The floW of fluid is restricted by valve 54 and also by restrictor 72 to provide a low speed of lowering. Connected in parallel with valve 74 and flow restrictor 72 by means of a conduit 76 is another solenoid operated normally closed valve 78. When valve 78 is energized to open, flow restrictor 72 is by-passed so that there is less restriction to fluid flowing out of motor 24 with the result that motor 24 can retract at a greater speed for a given load on upright 22.

Referring now also to FIG. 3, it will be seen that motor 58 which d.ives pump 56 can be connected in circuit with battery 20 by means of a normally open solenoid operated switch 80. Similarly, motor 68 which drives pump 62 can be connected in circuit with battery 20 by means of a normally open solenoid actuated switch 82.

The system for controlling upright 22 includes a first circuit 84 in which switch 50, a normally closed switch 86, a diode 88, a normally open operator controlled switch 90 and the solenoid 92 which actuates switch 80 are all connected in series. Switch 86 is mounted on mast 26 (as shown in FIG. 1) and is actuated to open by means of a cam 94 mounted on intermediate slide 28. Switch 86 and cam 94 are located preferably so that switch 86 opens when there are about 6 inches of extension remaining out of the total possible extension of upright 22. Diode 88 is disposed in circuit 84 so that current can flow only in the direction from switch 86 toward switch 90.

The upright control system also includes a second control circuit 96. Control circuit 96 is connected to circuit 84 between switch 86 and diode 88, as shown, and includes a normally open operator controlled switch 98, a normally open time delayed solenoid actuated switch 100 and the solenoid 102 for actuating switch 82 all connected in series. Circuit 96 also includes a circuit 104 which connects the solenoid 106 of switch 100 in parallel with solenoid 102. Also, a diode 108 is connected between circuit 104 of circuit 96 and circuit 84 so that current can flow only from circuit 104 to circuit 84. Thus, when switch 98 is closed, assuming that switches 50 are closed and switch 90 is open, solenoid 92 is energized so that switch 80 is closed and motor 58 is connected in circuit with battery 20. At the same time solenoid 106 is energized tending to close switch 100; however, closing of switch 100 is delayed because it is a time delay switch, and thus closes later than switch 80. When switch 100 does close solenoid 102 is energized which then closes switch 82 and thus connects motor 68 in circuit with battery 20. As a result of this arrangement it is always necessary to go through the low speed extension of upright 22 before the high speed extension of upright 22 can be reached.

Further, the upright control system includes a third control circuit 110 which is connected to control circuit 84 between diode 88 and switch 90, as shown, and includes normally open switches 112 and 114 connected in series. Circuit 110 also includes a solenoid 116 which when energized opens valve 74. Connected in parallel with solenoid 116 is a normally open solenoid actuated time delay switch 118 and a solenoid 120 which are connected in series with each other. When energized solenoid 120 actuates valve 78 to open. Also connected in parallel with solenoid 116 is a solenoid 122 which, when energized, actuates switch 118 to close. Thus, assuming switches 50, 86, 112 and 114 are closed, solenoid 116 will be energized to actuate valve 74 to open, thereby permitting fluid motor 24 to retract at a low speed. Because solenoid 122 is energized at the same time as solenoid 116, switch 118 will be actuated to close, but it will not close until some time interval following energization of solenoid 116 because it has a built in time delay. When switch 118 does close solenoid 120 will be energized so that valve 78 will be actuated to open. Fluid motor 24 will now be able to lower at a greater rate of speed. At this point it will be clear that whenever fluid motor 24 is lowered that it must always start lowering at its lowest speed, and then following a time delay can lower at a higher rate of speed.

Switch 112 is mounted on operators station 34 which in turn is mounted on carriage 32 and is actuated to close by means of a cam 122 which is mounted on inner slide 30. Switch 112 and cam 122 (FIG. 1) are disposed preferably so that .when operators station 34 (FIG. 1) has been raised about 18 inches due to extension of upright 22 switch 112 will close.

Finally, the system for controlling upright 22 includes a bypass circuit 124 which is connected at one end to battery 20 and at the other end thereof to circuit 110 between switches 112 and 114. Circuit 124 includes a normally open operator controlled switch 126.

In order to enable persons skilled in the art to better understand my invention, I will now explain the operation of it. It will be assumed that an operator is standing at operators station 34 on platform 38 and depressing pedal 48 so that switch 50 is closed. Now if the operator desires to elevate operators station 34 and load engaging forks 36 at a low speed he needs merely to close switch which will energize solenoid 92, causing switch 80 to close and thereby connect motor 58 in circuit with battery 20 so that motor 58 will drive pump 56 which will supply pressurized fluid to fluid motor 24 causing it, and thereby upright 22 to extend. After upright 22 has extended a predetermined distance, preferably about 18 inches from its lowermost position, switch 112 will be actuated to close by cam 122. If the operator wishes to extend the upright at a greater speed he closes switch 98 with the result that, following a time delay built into switch 100, solenoid 102 will be energized with the result that switch 82 will be closed so that motor 68 will be connected in circuit with battery 20 thereby driving pump 62 with the result that the output of both pumps 56 and 62 will be supplied to fluid motor 24 so that it will extend at a greater rate of speed. When upright 22 has been extended to within 6 inches of its full extension cam 94 will engage switch 86 and cause it to open with the result that both solenoids 92 and 102 are de-energized so that the circuits for motors 58 and 68 are opened due to switches 80 and 82 opening. In order to extend the upright fully through the last 6 inches of extension the operator must now close switches 126 and 90. When this is done switch 86 is bypassed and solenoid 92 again can be energized so that switch 80 is closed, thereby placing motor 56 in circuit with battery 20 so that pump 56 is again being driven to supply pressurized fluid to motor 24. It will be noted, however, that it is not possible to energize solenoid 102 in this condition of operation. Thus, the last 6 inches of extension can be made at low speed only. It should also be noted that in this condition of operation the switch 50 which is associated with pedal 48 also is bypassed.

In order to lower upright 22 from any point of extension above which switch 112 is closed and below which switch 86 is opened the operator merely needs to close switch 114 which results in energizing solenoid 116 to operate valve 74 to open so that upright 22 can lower at a low rate of speed, and then following a time delay due to the time delay built into switch 118, solenoid 120 will be energized to operate valve 78 which bypasses flow restrictor 72 so that upright 22 can lower at a higher rate of speed. In order to lower upright 22 when it has been raised above the point at which switch 86 is opened it is necessary to close both switches 126 and 114. In order to lower upright 22 below the point at which switch 112 opens it again is necessary for the operator to close both switches 126 and 114. The time delay built into switch 118 is long enough so that by the time switch 118 can close to thereby provide the higher speed of lowering the upright has lowered the last 18 inches or so to the floor.

While only a single embodiment of my invention has been described, it will be understood that the detailed description is intended to be illustrative only and that various changes and modifications can be made to my invention without departing from the spirit or scope of it. For example, while the control system has been described as electrical it could be hydraulically or pneumatically operated also. Consequently, the limits of my invention should be determined from the appended claims.

What is claimed is:

1. For use with a lift truck having a power source. a fluid reservoir, an extendible upright including a fluid motor, first means for operating the fluid motor to extend the upright at a given speed, second means for operating the fluid motor to extend the upright at a speed different from the given speed, and means for communicating the fluid motor with the reservoir for lowering the upright, an upright control system comprising a first control circuit connected to the power source and the first operating means for actuating the first operating means to extend the upright, the said first circuit including means responsive to upright extension for deactuating the first operating means when the upright is extended a predetermined distance, a second control circuit connected to the said first circuit and the second operating means for actuating the second operating means to extend the upright, a third control circuit connected to the said first circuit and the lowering means for actuating the lowering means to connect the fluid motor with the reservoir for lowering the upright, a fourth control circuit connected to the power source and the said third circuit for bypassing the said deactuating means, and means disposed in the said first circuit between the said second and third circuits for permitting power flow in the said first circuit between the said second and third circuits from the said second circuit to the said third circuit only.

2. An upright control system as set forth in claim 1 wherein the said third circuit includes means disposed between the said first and fourth circuits and responsive to upright extension for deactuating the said lowering means when the upright is lowered a predetermined distance.

3. An upright control system as set forth in claim 1 wherein the said second circuit includes means for delaying actuation of the second operating means and including means connected between the said first and second circuits for permitting power flow from the said second circuit to the said first circuit only.

4. An upright control system as set forth in claim 1 wherein the said first circuit includes operator controlled means for deactuating the operating means.

5. An upright control system as set forth' in claim 2 wherein the said second circuit includes means for delaying actuation of the second operating means and including means connected between the said first and second circuits for permitting power flow from the said second circuit to the said first circuit only.

6. An upright control system as set forth in claim 5 wherein the said one-way power flow means are diodes.

7. An upright control system as set forth in claim 5 wherein the said first circuit includes operator controlled means for deactuating the operating means.

8. For use with a lift truck having a power source, a fluid reservoir and an extendible upright, the combination comprising a fluid motor connected to the upright for extending the upright, first means for operating the said fluid motor to extend the upright at a given speed, second means for operating the said fluid motor to extend the upright at a speed different from the given speed, first means for communicating the fluid motor with the reservoir for lowering tthe upright at a given speed, a first control circuit connected to the power source and the said first operating means for actuating the said first operating means to extend the upright, the said first circuit including means responsive to upright extension for deactuating the first operating means when the upright is extended a predetermined distance, a second control circuit connected to the said first circuit and the second operating means for actuating the second operating means to extend the upright, a third control circuit connected to the said first circuit and the said first lowering means for actuating the said lowering means to connect the fluid motor with the reservoir for lowering the upright, a fourth control circuit connected to the power source and the said third circuit for bypassing the said deactuating means, and means disposed in the said first circuit between the said second and third circuits for permitting power flow in the said first circuit between the said second and third circuits from the said second circuit to the said third circuit only.

9. The combination as set forth in claim 8 wherein the said third circuit includes means disposed between the said first and fourth circuits and responsive to upright extension for deactuating the said first lowering means when the upright is lowered a predetermined distance for actuating the said first lowering means.

10. The combination as set forth in claim 9 wherein the said second circuit includes means for delaying actuation of the said second operating means and including means connected between the said first and second circuits for permitting power flow from the said second circuit to the said first circuit only.

11. The combination as set forth in claim 10 and including second means for communicating the fluid motor with the reservoir for lowering the upright at a speed different from the given lowering speed and a fifth control circuit connected to the said third control circuit and the said second lowering means for actuating the said lowering means, the said fifth circuit including means for delaying actuation of the said second lowering means.

References Cited UNITED STATES PATENTS 2,359,112 9/1944 Hymans. 3,016,973 1/1962 Williamson. 3,135,357 6/1964 Hastings 1879 3,213,967 10/1965 Hastings et a1 187-9 3,443,380 5/ 1969 Karazija.

EDGAR W. GEOGHEGAN, Primary Examiner US. Cl. X.R. l879 @2 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,486,333 Dated D cem er 30, 1969 Inventoz-(s) Henry J. Thomas It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The patent is assigned to Clark Equipment Company, A Delaware Corporation rather than a Michigan Corporation Col. 2, line 15 "manpulation" should be manipulation Col. 3, line 26, add and 86 after "50" and before "are".

Claim 9, line 26, C01. 6, "actuating" should be deactuating sumo AN-u SEALED JUL 211970 .SEAL Attest:

win-um E. 50mm. JR-

Mtestin Offi 

